While the adjustable mount of the present invention is described relative to use in a laser system, it will be apparent from the description that the precise positioning capability and relative simplicity of construction make the present mount widely applicable wherever adjustable mounts can be used.
In laser systems, it is critical that the propagating beam be precisely aligned. Alignment may involve both detection of the beam path and adjustment of that path. For example, copending commonly assigned Cutbruth U.S. patent application Ser. No. 573,251, filed Jan. 23, 1984, now abandoned entitled "Three-Point Spherical Mirror Mount", discloses a concurrently developed mirror mount for precisely adjusting mirrors to the desired orientation. In one aspect, this mirror mount uses a three-point mounting system to thereby eliminate the prior art requirement of perfectly machining and aligning the spherical inner ring mirror mount and the mating outer spherical housing.
The present invention relates specifically to adjustable mounts or stages which mount electromagnetic sensors that detect the laser beam position. As shown in FIG. 1, a typical prior art stage 10 includes a metal center block 11 which is slidably mounted on a pair of side ball bearing assemblies 12--12. A laser beam (not shown) is transmitted through the center hole 13 and detected by an electromagnetic device (not shown) located in or aligned with the center hole. The center block 11 is also slidably mounted on a pair of frame guide shafts 14--14 for reversible position adjustment, as indicated by arrow 15. A micrometer-type adjuster 16 is mounted to frame end rail 17. Upon inward rotation, the adjuster 16 pushes against the left side of center block 11 and thereby moves the block to the right, against the biasing action of shaft-mounted compression springs 18--18. When the micrometer adjuster 16 is retracted, the biasing springs 18--18 move the center block in the opposite, leftward direction.
Like the prior art conventional spherical mirror mounts discussed in my above-mentioned patent application, the prior art stage 10, FIG. 1, must be machined with extremely high precision to provide the necessary accuracy and stability. Specifically, the side V-grooves 21 in the center stage 11 mate with the ball bearing assemblies 12, which themselves are mounted in V-shaped grooves in the side rails 23. Stability and accuracy not only require that the ball bearing assemblies 12 be perfectly true, but also require that all of the four V-groove surfaces associated with each ball bearing track 22 be perfectly parallel. This, of course, requires machining precision which is essentially impossible to achieve. However, if this level of machining precision is not achieved, the smallest surface irregularities and protrusions relative to parallelism may be the sole support point for the center block and thus act as an unstable pivotal mounting point.
Guide shafts 14--14 somewhat counteract this lack of stability and accuracy. In addition, the pair of side rails 23--23 mount the ball bearing assemblies 12 and in turn are mounted by screws 24 to the frame base 26 for lateral position adjustment by screws 27--27 which are secured in the fixed frame sides 28. The adjustment screws 27--27 compensate somewhat for deviations from parallelism in the center block groove 21 and in the ball bearing retainer groove. However, the adjusting screws introduce an undesirable stress into the stage components. Furthermore, the combination of the guide shafts 14--14 and the position-adjustable side mounting rails 23--23 cannot fully compensate for the inherent instability in the described ball bearing mounting arrangement.
In addition, the side rails 23--23 and the guide shafts 14--14 limit the area which is available for the laser aperture 13. This is important because, preferably, the laser aperture is large and encompasses a large proportion of the surface area of the center block 11. The reason is simple. For a laser beam of a given energy, a relatively large beam cross-section is usually easier to control and causes less damage to the optics system components than does a smaller, more intense beam. However, the size of the stage 10 and the center block 11 are limited by the relatively complex construction of the stage and, in particular, by the above-mentioned difficulty in precisely fabricating the center block and side rail grooves. Furthermore, the amount of the available stage surface area which could be used for the laser hole 13 is decreased by the stability-compensating guide shafts 14--14 and side rails 23--23, with the end result, shown in FIG. 1, that only a small percentage of the available center block area can be utilized for the laser transmission hole 13.